This invention relates to the removal and recovery of waste oil or other petroleum hydrocarbons from substrates, particularly the non-destructive removal of such waste products.
When petroleum hydrocarbons, such as motor oil, brake fluids, heating oils and the like, are deposited on a porous or non-porous substrate, it adheres to the surface. This results in a contaminated substrate with undesirable environmental and commercial effects.
In the first instance, where the contaminated substrate is no longer useful for its original purpose, such as in the case of oil tanks for heating oil, the resulting contaminated material is not recyclable and the used tanks are stored in a dump. If conventional methods and chemicals were to be used to clean the tanks, the resulting hazardous and toxic effluent would need to be incinerated or land filled, which only relocates the pollution.
In the second instance, where the removal and relocation of the substrate is not possible or feasible, such as in the case of driving and parking surfaces for motor vehicles, the petroleum deposits on the surfaces are washed away by rain water or wash water, resulting in pollution. Removal of the accumulated hydrocarbons using conventional methods and chemical degreasers results in chemical mixtures of questionable or undetermined properties that are not recyclable or illegal to discharge. In this instance, the effluent must be relocated, which results in simply transferring the pollution from one location to another. This detracts from the commercial viability of the process.
If a surface has high porosity (such as asphalt), typically a solvent, such as gasoline, kerosene or mineral spirits, can be employed to remove a petroleum hydrocarbon deposit, hereinafter simply referred to as xe2x80x9coilxe2x80x9d. If adhesion of the oil to the surface has occurred, the solvent must be of sufficient strength to dissolve the oil and penetrate to the substrate. Apart from creating a fire hazard, there are three inherent problems associated with this method. The first is that when attempting to remove refined petroleum hydrocarbon from an asphalt surface, the solvent used must be of sufficient strength to penetrate the surface deposit. As a result, the strong solvent emulsifies a large part of the asphalt along with the deposit and leaves a residue that can become flammable. Technically, this is considered destructive removal, and will contribute to accelerating the breakdown of the asphalt as well as acting as a bond breaker if a coating or sealant is to be applied to the surface after cleaning. The second problem is that the resulting effluent may not be recyclable depending on the solvent. The third problem is that the solvent will disperse the hydrocarbon and leave a residue. It does not suspend the hydrocarbon to allow for removal. In the case of asphalt, a large stain will be apparent after washing, requiring further treatment for removal.
The same problems that occur with the above solvents occur with commercially available degreasers and detergents. However, typically these products are not of sufficient strength to penetrate the oil and thus overcome the adhesion of the oil to the surface.
Acids, bleaches, paint strippers contaminate the waste effluent beyond repair and are not recyclable.
It is an object of the present invention to alleviate the above-mentioned difficulties.
According to the invention there is provided a method of non destructive recovery of a petroleum hydrocarbon from a contaminated substrate, comprising the steps of separating the hydrocarbon substantially intact from the substrate by applying a hydrocarbon removing agent comprising an aqueous solution of an alkali and a surfactant to the substrate; and collecting the hydrocarbon separated from the substrate.
Also according to the invention, there is provided a method of non destructive recovery of a petroleum hydrocarbon from a contaminated substrate, comprising the steps of separating the hydrocarbon substantially intact from the substrate by applying a hydrocarbon removing agent to the substrate; and collecting the hydrocarbon separated from the substrate, wherein said separating the hydrocarbon from the substrate comprises the steps of applying a separation agent to the substrate to effect adhesion failure of the hydrocarbon, thereby to release the hydrocarbon intact from the substrate; and applying a surfactant to suspend the hydrocarbon removed from the substrate; said separation agent and said surfactant collectively comprising said hydrocarbon removing agent.
Further objects and advantages of the invention will become apparent from the description of preferred embodiments of the invention below.